Percolator
also: coffee percolator, stovetop percolator
An old stovetop brewer that recirculates boiling water through the grounds, often tasting bitter.
Percolator is a traditional stovetop (or electric) brewer that cycles boiling water repeatedly through a basket of grounds. Heat sends water up a central tube, it splashes over the bed, drains back down, and the cycle repeats until you pull it off the heat.
Why it matters: two things work against it. First, the water is boiling, hotter than the roughly 90 to 96 C (195 to 205 F) range that brews coffee well. Second, the same water passes through the grounds again and again, so already-extracted coffee keeps getting re-extracted. Together these push toward over-extraction, which is why percolator coffee has a reputation for tasting bitter and harsh. See why coffee tastes bitter.
How it shows up: strong, dark, often a little burnt, with a heavy body but blurred flavor. It can be tamed with a coarse grind and a short brew time, watching closely and removing it from the heat the moment it is done. It is mostly a nostalgic or camping method now, largely replaced by drip machines and, for a similar stovetop spirit, the cleaner moka pot.